Compostable packaging for containment of liquids

ABSTRACT

A compostable paperboard container and package for liquids which is coated with a material capable of degrading to carbon dioxide, water and biomass under composting conditions.

This is a division of application Ser. No. 07/962,100, filed Oct. 16,1992 abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a compostable container for containingliquids or liquid containing materials. The present invention furthersrelates to a paperboard container having a degradable coating on atleast one of the internal or external surfaces thereof. Moreparticularly, the present invention relates to a paperboard containerwhich will biodegrade to carbon dioxide, water and biomass undercomposting conditions. The present invention further relates to a methodof making and a method of using the degradable container.

2. Discussion of the Prior Art

In the management of Municipal Solid Waste (MSW), the expectation thatpaper and paper products would biodegrade in landfills has proven to beunreliable. In fact, newspapers buried for over fifty year have beenrecovered from landfills in readable condition. Since paper comprisesabout 50 % of landfill space, it has become an important priority tofind alternate ways to manage paper waste.

Recycling paper, often with the removal of printing inks and coatings,has proven to be economically feasible when the recovered pulp fibersfind new markets and applications. Fiber recovery, and, in particular,repeated fiber recoveries tend to damage, break, and otherwise reducethe quality of paper fiber. This degradation in paper quality oftenresults in a product with limited or nonexistent new markets orapplications.

Since paper has the inherent property of biodegradability underappropriate conditions, more attractive alternates to simple landfillinghave received increased attention. Among these, is the process ofcomposting, in which waste is degraded to humus or biomass underaccelerated and controlled conditions of moisture, air andmicroorganisms. More specifically, paper, under composting conditions isconverted into carbon dioxide, water, and biomass. The biomass isessentially comprised of microorganisms. Thus, the mass of waste issignificantly reduced and the humus by-product has commercial value aslow grade fertilizer, soil conditioner, and as a mulch for land andagricultural applications.

Paper products are often coated with resins or plastic materials toprovide barrier properties when they will be used in the containment ofliquids. The most important requirements for these structures whenintended for use as folded cartons to contain liquid products include:

a. barrier properties to reduce and prevent absorption and/ortransmission of liquid components;

b. heat sealability for carton construction and integrity.

c. printability to provide attractive, non-functional graphics;

d. vapor barriers to contain fragrances, flavors, moisture, etc.;

e. barriers to oxygen and other ambient gases;

f. rigidity, shape retention, and crush resistance.

Typical constructions of important commercial value include milk cartonsin which the paperboard coating composition is low density polyethylene;fruit juice containers as described in U.S. Pat. No. Re 33,376; and wetwipe container as described in copending U.S. patent application Ser.Nos. 07/740,141 now abandoned and 07/923,556, now U.S. Pat. No.5,286,538 all of which are incorporated herein by reference.

Such constructions meet the requirements stated above in (a)-(f),however, such constructions are compostable only to the degree to whichcellulose pulp is present, typically around 85% Under compostingconditions, the pulp fibers would be expected to decompose leaving aresidue of biologically inert plastic.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to overcome these and otherdifficulties encountered in the prior art.

Given the current waste disposal problems, another object of the presentinvention is to provide a container for liquids which meets requirements(a)-(f) and which will also degrade to carbon dioxide, water and biomassunder composting conditions.

Another object of the present invention is to provide liquid barrierproperties to pulp based substrates which are degradable undercomposting conditions by coating with polymers selected from the groupof aliphatic polyesters.

A further object of the invention is to provide, as an environmentallyimproved alternate to plastic, a completely degradable packagingmaterial for the containment of liquids and wet products.

Still another object of the invention is to provide crush-resistant,durable packaging material suitable for liquids and wet products.

A further object of the invention is to provide coated packagingmaterial for use in folded cartons in which the coating has a compostingrate approximately equal to the pulp based substrate.

Another object of the invention is to provide special properties tocoatings of biodegradable aliphatic polyesters, by blending to about 30%by weight with polymers or fillers that are either miscible ormechanically compatible.

To achieve the objects and in accordance with the purpose of theinvention, as embodied and broadly described herein, the inventioncomprises a compostable package for containing liquids or wet productsincluding a base of paperboard having coated thereon a polymericmaterial capable of preventing leaks wherein said base and saidpolymeric material degrades to form carbon dioxide, water and biomass.

In another aspect of the invention there is provided a method of makinga compostable package for containing a liquid or a liquid containingmaterial comprising, providing a base of paperboard, coating saidpaperboard with a material capable of preventing leaks, wherein saidbase and said material are compostable to carbon dioxide, water andbiomass, forming said paperboard into a container and sealing the edgesand bottom of said container.

In still another aspect of the invention there is provided a method ofusing a compostable package for containing a liquid or a liquidcontaining material comprising, providing a base of paperboard, coatingsaid paperboard with a material capable of preventing leaks, whereinsaid base and said material are compostable to carbon dioxide, water andbiomass, forming said paperboard into a container, sealing the edges andbottom of said container, and placing into said container a liquid or amaterial containing a liquid.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, illustrates the aerobic biodegradation of polycaprolactone usingASTM D5209.

FIG. 2, illustrates the loss of mechanical properties observed for afilm of polycaprolactone under outdoor composting conditions.

FIG. 3, illustrates the loss of mechanical properties observed for afilm of polycaprolactone under indoor composting conditions.

FIG. 4, illustrates the biodegradability mechanism for polycaprolactone.

FIG. 5, illustrates the biodegradations of polyesters of3-hydroxybutyric acid and 3-hydroxyvaleric acid (PHBV).

FIG. 6, illustrates the aerobic biodegradation of blends ofpolycaprolactone and polyethylene.

FIG. 7, illustrates the loss of mechanical properties observed for afilm of polycaprolactone-polyethylene blends under outdoor compostingconditions.

FIG. 8, illustrates the loss of mechanical properties observed for afilm of polycaprolactone-polyethylene blends under indoor compostingconditions.

FIGS. 9-12, illustrate cross-sectional views of the structure of thecontainer materials according to the present invention.

FIG. 13, illustrates the apparatus for use in the test methodologyemployed in the examples.

DESCRIPTION OF THE INVENTION

According to the present invention, a paperboard container is producedfor containing liquids or liquid containing materials. The container isformed from paperboard or related paper substrates. For the purposes ofthis invention, the term paperboard refers to those grades and types ofpaper made on either cylinder board machines or multiwire, fourdriniertype machines as well as multiformers. Fiber stock may be eitherrecycled, or virgin or mixtures thereof, bleached or unbleached.Additional information on paper and paperboard used in packagingapplications may be found in James E. Kline, Chapter 10, Paper andPaperboard, Miller Freeman Publications, San Francisco, Calif., 1982,which is herein incorporated by reference.

The paperboard or paper substrate for use in the present invention has abasis weight of from about 35 lbs/ream to about 220 lbs/ream andpreferably from about 175 lbs/ream to about 220 lbs/ream. According toone embodiment of the present invention, the paper substrate has athickness from about 4 to 25 mils and more preferably about 10 to 20mils. The coated paperboard should be selected to produce a containerhaving a cross directional (CD) stiffness as determined by the Tabermethod of from 50 to 150 and more preferably of from 60 to 135. TheTaber method is described in TAPPI Test Procedure T-489.

The ratio of cross direction Taber stiffness of the coated paperboard toits basis weight (lb/ream) is at least 0.20 and more preferably at least0.5.

Paperboard is generally stronger and stiffer in the machine direction(MD) than in the cross direction. According to one embodiment of thepresent invention the machine direction preferably runs along thecontainer from side to side, i.e. in a direction perpendicular with thetop and bottom of the container. The machine direction runs from side toside of the container; the fiber direction of the paperboard from top tobottom of the container is said to be the cross direction (CD). Thecoated paperboard used in the container according to the presentinvention preferably has a ratio of Taber stiffness of MD/CD of lessthan or equal to about 2.65 and more preferably less than or equal toabout 1.92.

The paperboard or paper substrate material is coated on at least oneside thereof with a degradable resin in a thickness of from about 5.5 to2.0 mils. In one preferred embodiment, both sides of the paperboardsubstrate are coated with the degradable resin to a thickness of fromabout 5.5 to about 2.0 mils. In the present invention degradationincludes biodegradation as well as degradation by moisture, light,oxygen and other well known means of breaking down waste materials.

Coating techniques, for example, extrusion coating, impregnation and thelike, are well known in the art, and in accordance with the presentinvention, inner coatings and outer coatings may be applied by processeswell known in the art. Furthermore, the design, quality control andfabrication of folded cartons for the containment of liquids are wellknown in the art, and these processes and techniques may be used inmaking the containers of the present invention.

Characteristics of the biodegradable coating materials for use in thepresent invention include good moisture barrier properties, good thermalsealing properties, sufficient stiffness to give the container goodcrush resistance and biodegradability under composting conditions.

Examples of biodegradable resins include thermoplastic oxyalkanoylpolymers, e.g., ε-caprolactone polymers and those that contain therecurring unit: ##STR1##

Wherein x is an integer having a value of 2,3 and 5-7, includingpolymers of beta propriolactone and Δ-valerolactone; polyesters of3-hydroxybutyric acid, 3-hydroxyvaleric acid and mixtures thereof aswell as copolymers of any of the above.

Suitable also are graft polymers prepared by reacting a lactone such asε-caprolactone with hydroxyl or amino functional resins such ashydrolyzed ethylene-vinyl acetate copolymers; segmented polyurethaneprepared by reacting polycaprolactone bearing terminal hydroxyl groupswith diisocyanates and, optionally, chain-extending glycols such as 1,4butanediol.

Included also are aliphatic polyesters such as polyglycolic acid,polylactic acid, polydioxanone, poly(trimethylene carbonate) and theirco- and terpolymers as well as blends of any of the above withpolyesters prepared from alkanediols and alkanedicarboxylic acidsincluding oxalates.

Preferred biodegradable resins for use in the present invention arepolyhydroxyaliphatic acids (PHAA).

Naturally occurring biodegradable substances are useful as fillersoffering the advantage of reduced cost. Such fillers include starch,tree bark, ground paper, peat moss and soy bean powder.

Polyhydroxyaliphatic acids in film form are biodegradable undercomposting conditions. One preferred polyhydroxyaliphatic acid,polycaprolactone (PCL) is available as a biodegradable thermoplasticresin from Union Carbide. It is synthesized from ε-caprolactone:##STR2## Polycaprolactone in film form, has been demonstrated to bebiodegradable under soil burial and composting conditions, as shown inFIGS. 1-3. Composting of PCL is thought to occur by the mechanismproposed in FIG. 4.

Other preferred polymers for use in the present invention are thecommercially available PHBV polymers of ICI which are polyesters of3-hydroxybutyric (HB) and 3 hydroxyvaleric (HV) acids. Their generalstructure is: ##STR3## These polymers are produced by the fermentationof sugar by the bacterium ALCALIGENES EUTROPHUS and will degrade tocarbon dioxide and water when placed in the presence of microorganismsfound in soil, sewage, and river bottoms as shown in FIG. 5.

while PCL is claimed to undergo aerobic degradation, PHBV will degradeunder either aerobic or anaerobic conditions.

To enhance or optimize functional properties and cost it may bedesirable to blend these resins with other material. The successfulblending of the aliphatic polyester with additives to provide improvedproperties and reduced cost without impairing degradability was a mostuseful and surprising aspect of this invention.

Additives and blending resins include those which are either miscible ormechanically compatible with aliphatic polyester. Examples listed beloware suitable for use with polycaprolactone:

    ______________________________________                                        Miscible           Mechanically Compatible                                    ______________________________________                                        PVC                Polyethylene                                               SAN                Polypropylene                                              ABS                Natural Rubber                                             Phenoxy            Styrene/Butadiene                                          Polycarbonate      Elastomer & Block                                                             Copolymers                                                 Nitrocellulose     Polyvinylacetate                                           Poly (Vinylidene Chloride)                                                                       Polybutadiene                                              Styrene/Allyl Alcohol                                                                            Ethylene/Propylene                                         Copolymers         Rubber                                                     ______________________________________                                    

In addition, PCL may be blended with thermoplastic elastomers forimproved toughness, adhesive, and flexibility. Especially suitable arethe elastomeric segmented polyurethanes prepared from aliphaticpolyester diols, aromatic or alicyclic diisocyanates; and, optionally,short chain diol or diamine chain-extender.

Accordingly, the skilled artisan can incorporate the many useful andunique properties of these additives into the coating composites to meetspecific requirements of the various end uses contemplated. Thesematerials may be added in from about 0% to about 30%, preferably fromabout 10 to about 20%. Although these materials alone are either slowlycompostable or noncompostable, their use in limited amounts as describedabove does not impair the ultimate biodegradation of the coatingmaterials.

In addition to blended compositions, these compositions may be coatedonto the paperboard substrate in successive layers. Noncompostable orslowly compostable layers are so positioned so as not to interfere withcomposting of the remainder of the container. As an alternative,individual layers of the same or different blended materials may be usedto form the substrate coatings. Noncompostable and slowly compostablematerials may be used in blends or as intermediate layers in limitedamounts. When used in blends, these materials are preferably containedin less than 30% and when found in film form are preferably less than0.6 mils in thickness. These materials do not interfere with thecompostability and degradation of the container and are found in thehumus. After composting, these materials are from a practical standpointindistinguishable from the rest of the humus.

In one preferred embodiment, the coating is comprised of either 100%aliphatic polyester or mixtures thereof with polyethylene in which thepolyethylene is present at levels up to about 30%. The addition ofpolyethylene reduces the rate of water vapor transmission which isadvantageous for certain long shelf-life products. With the addition ofas much as 30% polyethylene to aliphatic polyester, composting isslower, but nevertheless effective under typical composting conditions,as shown in FIGS. 6-8.

As an alternative or in addition to the materials described above,starch may be added to the coating materials according to the presentinvention. Starch may be added in from about 0% to about 70% and morepreferably from about 40 to about 60%. One commercially available starchbased biodegradable material for use in the present invention isMater-Bi® produced by Novamont. This product contains up to 60% starchand 40% of a biodegradable resin material.

Since both coatings and pulp-based substrate are degradable, disposablepackages from these composites will decompose completely thuscontributing to alternate waste treatment of paper based products. Inaddition to being completely degradable, the containers according to thepresent invention may be incinerated.

FIGS. 9, 10, 11, and 12 show several embodiments of the coatedpaperboard used in the production of the container according to thepresent invention.

In FIG. 9, layer 1 is a flexible, strong paper substrate. Layer 2 is aninterior or exterior coating of 80-100% of a biodegradable resin havinga thickness of from about 5.5 to about 2.0 mil.

In FIG. 10, layer 1 is a paperboard substrate. An interior coating 2 andan exterior coating 3 are each present at a thickness of from about 0.5to about 2.0 mil.

When it is desirable to minimize the rate of water vapor transmission,the coated paperboard illustrated in FIG. 11 or 12 can be employed. InFIG. 11, a layer 4 comprising a barrier layer, for example a highpolyethylene content (30-100%) layer is coated directly onto one side ofthe paperboard. This coating is less than 0.5 mil. in thickness andpreferably about 0.2-0.3 mil.

In one preferred embodiment, coatings 2 and 3 are comprised of at least70% and preferably 90-100% of aliphatic polyester at a thickness of fromabout 0.5 to about 2 mils each. In addition to meeting all of therequirements described in (a)-(f) above, this embodiment provides anexcellent barrier to moisture vapor. The polyethylene component whichrepresents only about 1-3% by weight of the total composition does notinterfere with the rate of composting as it is confined to the innermostlayer and therefore does not hinder the degradation of the outermostlayers, i.e.: the aliphatic polyester or the cellulose pulp fibers.Thus, in this embodiment of the invention, the outer surfaces 2 and 3,which provide the initial sites for microbial attack, are composed ofthe biodegradable aliphatic polyester coatings. The pulp substrate 1 isaccessible to microbial attack either through the degraded layer 3 orthrough the edges.

In another alternative, the exterior coating layer 3 may be eliminatedin which case exposure of the pulp layer is immediate and direct.

FIG. 12 represents an alternate configuration to the performanceproperties and compostability of FIG. 10. In this particular case, thehigh barrier layer 4 is positioned between two layers of pulp substrate1 and 1'.

The container according to the present invention can be used to containa variety of liquids and liquid containing materials. For Example, thecontainer may be used for beverages such as milk, juice, fruit punch,soda, frozen juice, and iced tea; fabric softener; butter; margarine;cosmetics such as shampoo, conditioner, suntan lotion and body lotion;pancake syrup; cooking oil; processed grains, fruits and vegetables suchas applesauce and pasta sauces; frozen vegetables; fruits; breads andbread products and single-use wet wipes.

In one embodiment, the container which is preferable for use with thepresent invention has cut ends which are sealed to avoid seepage of theliquid into or out of the body of the paperboard. The sealing of theedges may be done in a variety of manners. It may be accomplished bycoating the edges, or by thinning the material down near the cut edges,i.e., skivving. Skivving of the edges is followed by folding the skivvedareas over the cut edges.

In another preferred embodiment, there is a moisture-impervious membraneprovided over the contents. Such membranes are sometimes referred to aslidding stock or material. Membranes for this application are typicallycomprised of a strong barrier top layer with a heat sealable lowerlayer. Non-limiting examples of top layers which may be used in thepresent invention, include paper, polyester, polyethylene, metallizedpolyester and polypropylene. Non-limiting examples of heat seal layersinclude polyethylene, ethylene-vinylacetate copolymers, and aliphaticpolyester. The edges of the membrane are adhered to the upper edges ofthe container and provide an effective storage and shipping seal. Themembrane should peel away from the edges of the container at the sealwithout exposure of pulp fibers. Additionally a moisture-imperviousmembrane can be heat sealed at the bottom of the container as well. Thebottom of the container is preferably heat sealed by applying heat andpressure, as well known in the art.

In one embodiment when the material to be contained is wet towellettes,the consumer obtains the product, rips open a perforation providing aslot or opening in the paperboard, permitting the hinged cap-like lid tobe raised. This exposes the membrane, which is easily peeled off withthe fingers and either stored in the box or thrown away. Thereafter,sealing is done entirely by the raising and lowering of the hinged lid.The moist towels or napkins are preferably stacked and lie horizontallyin the container and may be individually removed as needed.

It is also possible to provide a separate or separable pouch, bag orliner within the container to provide further waterproofing protection.Alternatively, this separable liner may be supplied during refilling ofthe container using a prepackaged bag of replacement wipes.

The container according to the present invention provides sufficientstiffness to provide the consumer with a container having handleabilityand to provide crush resistance of the box during storage, shipment andunder conditions of household use.

Containers according to the present invention preferably have acompression strength of at least 60 lbs. and more preferably at least 70lbs. as tested in accordance with TAPPI test procedure T-804. Thecontainer should also preferably have a cross directional Ring Crush ofat least 115 lbs. and more preferably at least 140 lbs. Ring crush canbe defined according to TAPPI Test Procedure T818 om-87. The compressionstrength of the containers is indicative of stacking and handlingability of the containers. Higher stiffness and crush resistance in thecross direction of the paperboard provides improved stacking andhandling of the containers.

The following examples are illustrative of the invention embodiedherein.

EXAMPLES

I. Paper used as base:

a. Bleached paperboard grade DLC (Schoeller Technical Papers, Pulaski,N.Y.); basis weight 175 lb/ream, 11.5 mils in thickness. Taber StiffnessMD (machine direction)×CD (cross direction)=65×35.

b. Bleached paperboard grade 4554 (Westvaco); basis weight 205 lb/ream;20 mil in thickness.

c. Bleached paperboard grade GAA-11 (Schoeller) 3.5 mil., 38 lb/ream.

d. Bleached paperboard 215 lb/ream, International Paper.

II. The coatings were extruded from the following polymers:

a. polycaprolactone (PCL) Tone Polymers P-767E and P-787 (representingdifferent molecular weights with 767E being the lowest), Union CarbideChemicals and Plastics Company, Inc., Solvents and Coatings MaterialsDivision, Bound Book, N.J.

b. PHBV tm (ICI Americas, Wilmington, Del.)--8% and 12%polyhydroxyvalerate;

c. Linear low density polyethylene (LLDPE); hexene based grade DFDA-7047(Union Carbide)

d. Low density polyethylene (LDPE) (Quantum)

III. Testing and Evaluations

a. Liquid containment was evaluated by the Mason Jar Test as follows:

The Mason Jar Test to Determine Liquid Containment of PackagingMaterials

This test procedure provides a convenient way to observe the liquidbarrier properties of film, paper, coated paper and related packagingmaterials. Failure in the test materials such as attack or penetrationby the contained liquid or leaks through pin-holes and other coatingimperfections are usually observed within the first 24 hours of thetest.

As can be seen from FIG. 13, a standard wide mouth Ball type Mason Jar,7 inch high and 31/2 inch wide is drilled with a 1/8" hole for pressureequalization.

The hole is plugged and the jar is filled with 600 ml of liquid.Optionally, dye may be added to aid in observing the nature and locationof failures.

Test specimen circles 3 and 5/16" in diameter are placed between tworubber gaskets and then tightened on the jar with the outer screw typelid supplied with the jar.

The jar is inverted and the plug removed.

The assembly is examined daily for signs of leakage and penetration.

In those cases where fluid consistently leaked around specimen edges, itwas useful to heat seal the material to the rubber gaskets.

Test results are reported based upon sample composition, thickness,liquid, elapsed time and nature of failure.

b. Water vapor transmission (WVT) was measured according to TAPPI T523on -87 and ASTM F 1249-90

c. Oxygen transmission was measured according to ASTM D-3985

Extrusion coatings were conducted using an Egan single flight screwthrough a 15 inch T-type die with a 30 mil gap setting.

Polycaprolactone P-767E was extruded with a temperature profile of 200°F. in the feed zone; 225°-250° F. in the barrel and 245° F. in the die.

Films were collected on a matte finished steel chill roll at 55°-60° F.and combined through a nip roll with the substrate after surfacetreatment of the latter with corona discharge or flame to enhanceadhesion.

EXAMPLE 1

PCL-767E was coated on one side of the Westvaco paperboard at athickness of 1.25 mils. The coated material was challenged with baby wetwipe lotion in the Mason Jar Test with no signs of penetration orleakage after one month. Its water vapor transmission rate was 15.65gm/100 sq. in./24 hr.

EXAMPLE 2

The coated paperboard from Example 1 was coated on the other side with asecond layer of PCL-767E at 1.25 mil.

The coated board basis weight was 311.5 g/sq.m. with a thickness of 23mils.

In the Mason Jar Test, using Downy® Fabric Softener, manufactured byProctor & Gamble, as the fluid, no leaks, swelling or penetration wasobserved after 1.3 months. Similar results were observed with iced teaover a period of 26 days. Water vapor transmission was 8.55 gm/100sq.in./24 hr.

EXAMPLE 3

PHBV 8% and 12% were mixed in a 1:1 ratio and extruded on the DLCsubstrate at a thickness of 1.5 mil. The basis weight of the coatedpaper was 215.8 g/sq.m.

In the Mason Jar Test, this material resisted leakage penetration bybaby wet wipe lotion for two months.

EXAMPLE 4

The coating mix of Example 3 was applied to one side of the DLCsubstrate at a thickness of 2.0 mil. Total basis weight was 241.8g/sq.m. The water vapor transmission value was 4.5 gm/100 sq.in./24 hr.

EXAMPLE 5

Polycaprolactone P-767E and LLDPE resin were mixed in a ratio of 90% PCLand 10% LLDPE and extruded onto the Westvaco paperboard at a coatingthickness of from about 1.0 to about 1.3 mil.

Extrusion temperatures were 275° F. at the feed zone 325°-345° F. in thebarrel; and 345° F. in the die.

Basis weight was 291.5 g/sq.m. Water vapor transmission was 11.0gm/sq.in./24 hr. In comparison to Experiment 1, water vapor transmissionwas reduced by 30% due to the presence of the polyethylene.

EXAMPLE 6

In this experiment a second coating layer was applied to the product ofExample 5. Coating thickness was 1.25 mil. and the basis weight measuredat 303.9 g/sq.m. Water vapor transmission was 5.33 gm/100 sq.in./24 hrs.In comparison to Experiment 2, water vapor transmission was reduced by38% due to the presence of polyethylene.

In the Mason Jar Test with baby wet wipe lotion, no leaks or penetrationwas observed for five weeks.

EXAMPLE 7

PCL-767E and LLDPE were mixed in a ratio of 85/15 and extruded onto theWestvaco paper at a thickness of 1.25 mil. Water vapor transmission was8.45 gm/100 sq.in./24 hr. In comparison to Experiment 1, water vaportransmission was reduced by 46% due to the polyethylene.

Downey fabric softener was used in the Mason Jar Test with no leaks orpenetration after one month.

EXAMPLE 8

A second layer of 85/15 PCL-767E and LLDPE at 1.25 mil. was applied tothe other side of the substrate used in Experiment 7 giving a totalbasis weight of 300.7 g/sq.m.

Water vapor transmission was 4.81 gm/100 sq.m./24 hr. In the Mason JarTest with baby wet wipe lotion, no leaks or penetration was observed forthree weeks. In comparison with Experiment 2, water vapor transmissionwas reduced by 44% due to the presence of polyethylene.

Example 1-8 above illustrate the configurations as set forth in FIGS. 9and 10.

EXAMPLE 9

With DLC as the substrate an 5.5 mil. coating of low densitypolyethylene (Quantum NA-206) was extruded on one side only.

Two layers of PCL 767E at 1.2 mil. each were then extruded onto first,the polyethylene side and second, the uncoated side. This composite isrepresentative of the embodiment described in FIG. 10. The water vaportransmission rate was 1.22 gm/100 in² /24 hr.

EXAMPLE 10

Example 9 was repeated with a polyethylene coating of 0.3 mil. The watervapor transmission rate was 1.79 gm/100 in² /24 hr. Taber Stiffnessaccording to TAPPI-489 was 98.5 in the machine-direction and 60.0 in thecross direction.

EXAMPLE 11

This is an example of the configuration shown in FIG. 8. The substrate,GAA-11, was a high tear strength, starch sized paper at 3.5 mil.thickness. It was extrusion coated with 2.0 mil. of PCL-767E giving amaterial useful as a heat sealable lidding stock.

The following examples illustrate test samples which were deemed toprovide acceptable barrier properties and degradation properties for usein the present invention.

EXAMPLE 12

2.0 mils of 85% PCL and 15% LLDPE was coated on both sides of a base of215 lb/ream paperboard obtained from International Paper.

EXAMPLE 13

1.25 mils of 85% PCL and 15% LLDPE was coated on both sides of a base of215 lb/ream paperboard obtained from International Paper.

EXAMPLE 14

2.0 mils of 90% PCL and 10% LLDPE was coated on both sides of a base of215 lb/ream paperboard obtained from International Paper.

EXAMPLE 15

1.25 mils of 90% PCL and 10% LLDPE was coated on both sides of a base of215 lb/ream paperboard obtained from International Paper.

EXAMPLE 16

First 0.5 mils of LDPE and then 1.25 mils of PCL were coated on one sideof a base of 215 lb/ream paperboard obtained from International Paper.The other side of the based was coated with 2.0 mils of PCL.

EXAMPLE 17

0.5 mils of LDPE, 85% PCL and 15% Texin 480A polyurethane was coated onboth sides of a base of 215 lb/ream paperboard obtained fromInternational Paper.

The oxygen permeability of these and other coatings on paperboard arecompared in the chart below (23° C.):

    ______________________________________                                                      CC O.sub.2 /100 IN.sub.2 /24 HOUR                               COATING SAMPLE  760 mm O.sub.2                                                                             0 mm O.sub.2                                     ______________________________________                                        Low density polyethylene;                                                                     21.8 (80% RH)                                                                              17.2 (80% RH)                                    reference Example 3                                                                           22.2 (30% RH)                                                                              17.3 (30% RH)                                    Serial No. 07/923,556                                                         Example 2       13.8 (80% RH)                                                                              12.6 (80% RH)                                    Present Invention                                                                             13.8 (30% RH)                                                                              12.4 (30% RH)                                    Example 6       29.0 (80% RH)                                                                              16.5 (80% RH)                                                    33.0 (30% RH)                                                                              43.0 (30% RH)                                    Example 8       26.0 (80% RH)                                                                              15.4 (80%)                                                       30.4 (30% RH)                                                                              28.5 (30% RH)                                    ______________________________________                                    

The coated paper board materials described in the examples above areexcellent candidates in the construction of containers for the packagingof liquids and wet products.

Ease of sealing and seal integrity were excellent, and surprisinglybetter than polyethylene which is the current industry standard. Whenexposed to hot air for 5-10 seconds, these coatings became tacky andreadily formed strong coating to coating or coating to paper bonds. Thepresent invention also provides for means by which theadhesive-properties of the coated surface may be modified. For examples,in the opening and dispensing of a heat sealed container, the adhesionmay be desirably reduced to allow a clean, fiber-free peel andseparation of layers.

These and related modifications may be achieved by blending or bytopical treatment of the coatings described herein with low molecularweight, (i.e., 500-3000) aliphatic polyesters. The later have a tendencyto be waxy and low in strength; and, as such, weaken the adhesiveinterface and lower the cohesive strength of the coating.

Materials of this invention are well suited to the steps involved inconverting coated paperboard into a folded carton including sheeting,printing, scoring, perforating, skivving, folding, and sealing.

The result of the Mason Jar Tests with typical fluids indicate thataliphatic polyesters in film form when coated on paper substrates areentirely satisfactory in containing a wide range of liquids.

Other embodiments of the invention will be invention will be apparent tothose skilled in the art from consideration of the specification andpractice of the invention disclosed herein. It is intended that thespecification and examples be considered as exemplary only, with a truescope and spirit of the invention being indicated by the followingclaims.

I claim:
 1. A compostable container for packaging a liquid or liquidcontaining material comprising:a base of paperboard having an exteriorsurface and an interior surface wherein at least said interior surfaceis treated with corona discharge or a flame; a coating of an aliphaticpolyester disposed on at least said interior surface at a thickness offrom about 5.5 mil to about 2.0 mils; wherein at least said treatedinterior surface and said coating define a water insensitiveinter-facial bond free of adhesive; wherein said base and said polyesterare capable of degrading at substantially the same rate to form carbondioxide, water, and biomass; and wherein said base has across-directional Taber stiffness of 50 to 150 , a thickness of fromabout 4 to 25 mils, and a basis weight of from about 35 to about 220lbs/ream.
 2. The container according to claim 1, wherein said polyesteris heat sealable, flexible, adhesive, resistance to stress cracks andabrasion resistant.
 3. The container according to claim 1, wherein saidaliphatic polyester is selected from the group consisting ofpolycaprolactone, a polyester of 3-hydroxybutyric acid, a polyester of3-hydroxyvaleric acid, polyglycolic acid, polylactic acid, andcopolymers and mixtures thereof.
 4. The container according to claim 3,wherein said polyester is polycaprolactone.
 5. The container accordingto claim 1 wherein said aliphatic polyester contains a blending polymerselected from the group consisting of PVC, SAN, ABS, phenoxy,polycarbonate, nitrocellulose, poly vinylidene chloride, styrene/allylalcohol copolymers, polyethylene, polypropylene, natural rubber,styrene/butadiene elastomer and block copolymers, polyvinylacetate,polybutadiene, ethylene/propylene rubber, starch and thermoplasticsegmented polyurethane.
 6. The container according to claim 5, whereinthe blending polymer is polyethylene.
 7. The container according toclaim 1, wherein said base further comprises, two layers of paperboardhaving a barrier layer placed therebetween.
 8. The container accordingto claim 7, wherein the barrier layer is polyethylene.
 9. The containeraccording to claim 1, wherein said base of paperboard has a barrierlayer applied prior to application of said polyester.
 10. The containeraccording to claim 9, wherein the barrier layer is polyethylene.
 11. Acompostable package having a liquid or liquid containing materialtherein comprising:a base of paperboard forming a container having anexterior surface and an interior surface wherein at least said interiorsurface is treated with corona discharge or a flame; a coating of analiphatic polyester disposed on at least said interior surface at athickness of from 5.5 mil to about 2.0 mils; wherein at least saidtreated interior surface and said coating define a water insensitiveinter-facial bond free of adhesive; wherein said base and said polyesterare capable of degrading at substantially the same rate to form carbondioxide water and biomass; wherein said base has a cross-directionalTaber stiffness of 50 to 150 , a thickness of from about 4 to 25 mils,and a basis weight of from about 35 to about 220 lbs/ream, and whereinsaid container has therein, a liquid or liquid containing material. 12.The container according to claim 11, wherein said polyester is selectedfrom polyhydroxyaliphatic acids.
 13. The container according to claim11, wherein said aliphatic polyester is selected from the groupconsisting of polycaprolactone, a polyester of 3-hydroxybutric acid, apolyester of 3-hydroxyvaleric acid, polyglycolic acid, polylactic acid,and copolymers and mixtures thereof.
 14. The container according toclaim 13, wherein said polyester is polycaprolactone.
 15. The containeraccording to claim 11, wherein said polyester further contains anadditive selected from the group consisting of PVC, SAN, ABS, phenyoxy,polycarbonate, nitrocellulose, poly vinylidene chloride, styrene/allylalcohol copolymers, polyethylene, polypropylene, natural rubber,styrene/polybutadiene, ethylene/propylene rubber and starch.
 16. Thecontainer according to claim 15, wherein the additive is polyethylene.17. The container according to claim 11, wherein the liquid or liquidcontaining material is selected from the group consisting of milk,juice, fruit punch, soda, frozen juice, iced tea, fabric softener,butter, margarine, cosmetics, shampoo, conditioner, suntan lotion, bodylotion, pancake syrup, cooking oil, processed grains, fruits,vegetables, applesauce pasta sauces, frozen vegetables, frozen fruits,breads, bread products and single-use wet wipes.
 18. The containeraccording to claim 17, wherein the liquid or liquid containing materialis single-use wet wipes.
 19. The container according to claim 11,wherein said base further comprises, two layers of paperboard having abarrier layer placed therebetween.
 20. The container according to claim19, wherein the barrier layer is polyethylene.
 21. The containeraccording to claim 11, wherein said base of paperboard has a barrierlayer applied prior to application of said polyester.
 22. The containeraccording to claim 21 wherein the barrier layer is polyethylene.